U.S. patent number 5,213,349 [Application Number 07/809,756] was granted by the patent office on 1993-05-25 for electrostatic chuck.
Invention is credited to Joe C. Elliott.
United States Patent |
5,213,349 |
Elliott |
May 25, 1993 |
Electrostatic chuck
Abstract
An electrostatic chuck for clamping a substrate during
manufacture thereof. The chuck has an electrostatic plate and a
support therefor. The electrostatic plate has a top surface, which
contacts the substrate, and which has an inner coil portion and an
outer coil portion for connection to a DC source for forming an
electric field. Heat in the substrate is removed by the plate. The
plate has a plurality of selectively placed chambers and passages
for removing heat by gas circulation therethrough.
Inventors: |
Elliott; Joe C. (Redwood City,
CA) |
Family
ID: |
25202149 |
Appl.
No.: |
07/809,756 |
Filed: |
December 18, 1991 |
Current U.S.
Class: |
279/128; 269/8;
361/234 |
Current CPC
Class: |
H01L
21/6831 (20130101); H01L 21/6833 (20130101); H02N
13/00 (20130101); Y10T 279/23 (20150115) |
Current International
Class: |
H01L
21/67 (20060101); H01L 21/683 (20060101); H02N
13/00 (20060101); H02N 013/00 () |
Field of
Search: |
;279/128,1M ;269/8
;361/234 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bishop; Steven C.
Attorney, Agent or Firm: Intellectual Property Law
Center
Claims
What is claimed is:
1. An electrostatic chuck comprising:
an electrostatic clamping and gas cooling plate; and
a support for the plate;
said plate having a top inner coil portion and a top outer coil
portion which can be respectively connected to a DC source for
forming an electrostatic field for clamping a substrate to the
plate during manufacture of the substrate;
said plate having a main body portion mechanically connected to the
inner coil portion and to the outer coil portion and respectively
forming an inner chamber and an outer chamber disposed under the
inner coil portion and the outer coil portion;
said main body portion having a bottom surface forming together
with the support a main chamber; and
said support and said plate having a plurality of passages
interconnecting the inner chamber and the outer chamber and the
main chamber for flow therethrough of gas.
2. The chuck of claim 1, wherein
the inner coil portion has an inner peripheral surface and an outer
peripheral surface for forming respectively an inner joint and an
outer joint for respective electrical insulating filler rings;
and
the outer coil portion has an inner peripheral surface and an outer
peripheral surface for forming respectively an inner joint and an
outer joint for respective electrical insulating.
3. The chuck of claim 1, wherein
the inner coil portion has an inner top surface;
the outer coil portion has an outer top surface; and
said top surfaces each have a plurality of radial slots and a ring
groove.
4. The chuck of claim 3, wherein
said inner coil portion and said outer coil portion each has an
inner diameter and an outer diameter and a ring-like shape; and
said main body portion has a top surface having an inner
ring-shaped recess receiving the inner coil portion and has an
outer ring-shaped recess receiving the outer coil portion.
Description
The invention generally relates to an electrostatic chuck, and in
particular the invention relates to an electrostatic substrate
chuck having a combination electrostatic clamping and fluid cooling
plate.
BACKGROUND OF THE INVENTION
The prior art electrostatic chuck is described in U.S. Pat. No.
4,184,188, issued Jan. 15, 1980. Related patents included U.S. Pat.
Nos. 4,949,783, issued Aug. 21, 1990 and 4,864,461, issued Sep. 5,
1989. A related publication is Wardly Electrostatic Wafer Chuck for
Electron Beam Microfabrication, 1506 Rev. Sci. Instrum., Vol. 44,
No. IV, October 1973.
The prior art electrostatic chuck includes a water cooled bottom
plate, an electrostatic plate supported by the water cooled bottom
plate, and a printed circuit capacitor supported by the
electrostatic plate and two sets of electrodes disposed on the
electrostatic plate and two sets of electrodes disposed on the
bottom silicone layer and a top silicone layer disposed on the two
sets of electrodes, whereby an electrostatic field can be formed
for clamping a substrate to the electrostatic plate and whereby
heat is conducted from the wafer to the water cooled plate.
One problem with the prior art electrostatic chuck is that the
operating voltage for forming a suitable chuck electrostatic field
is relatively high.
SUMMARY OF THE INVENTION
According to the present invention, an electrostatic chuck is
provided. This chuck comprises an electrostatic clamping and fluid
cooling plate for clamping and cooling a substrate, and a support
for the plate, said plate having a top inner coil portion and a top
outer coil portion with respective connections to a DC source for
forming an electrostatic field for clamping a substrate to the
plate during manufacture of the substrate, said plate having a main
body portion connected to the inner coil portion and to the outer
coil portion and respectively forming an inner circular chamber and
an outer circular chamber under the inner coil portion and the
outer coil portion, said main body portion having a bottom surface
forming a main fluid chamber together with the support, said inner
coil portion and said outer coil portion having respective
electrical insulation separators for electrical insulation from the
main body portion, said support and said plate main body portion
having gas passages for flow of gas through the chambers. The gas
is preferably helium, but argon or nitrogen may be used.
By using the inner core portion and outer coil portion, the
operating voltage for forming a suitable chuck electrostatic field
is minimized. By using the plate subassembly which has gas flow
chambers and passages, the thermal conduction is more effective.
The gas acts as a thermal media making a thermal connection between
the chuck and a substrate.
One object of the present invention is to provide an electrostatic
chuck which has a plate that has an inner coil and an outer coil
for forming its electrostatic field that uses a minimized operating
voltage.
Another object is to provide an electrostatic chuck which has an
electrostatic field forming plate that has integral gas chambers
and passages for maximized heat removal.
The foregoing and other objects, features and advantages will be
apparent from the following description of the preferred embodiment
of the invention as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of an electrostatic chick
according to this invention;
FIG. 2 is a section view as taken along the line 2--2 of FIG.
1;
FIG. 3 is a section view as taken along the line 3--3 of FIG.
2;
FIG. 4 is an elevation view as taken along the line 4--4 of FIG.
3;
FIG. 5 is a section view as taken along the line 5--5 of FIG.
1;
FIG. 6 is a section view as taken along the line 6--6 of FIG.
5;
FIG. 7 is an elevation view as taken along the line 7--7 of FIG.
6;
FIG. 8 is a section view as taken along the line 8--8 of FIG.
1;
FIG. 9 is a section view as taken along the line 9--9 of FIG.
8;
FIG. 10 is an elevation view as taken along the line 10--10 of FIG.
9;
FIG. 11 is an enlarged view as taken along the line 11--11 of FIG.
8;
FIG. 12 is a detail view of a portion of FIG. 1;
FIG. 13 is a top plan view of a support member as shown in FIG.
1;
FIG. 14 is a section view as taken along the line 14--14 of FIG.
13;
FIG. 15 is a section view as taken along the line 15--15 of FIG.
13;
FIG. 16 is a section view as taken along the line 16--16 of FIG.
13;
FIG. 17 is a section view as taken along the line 17--17 of FIG.
13; and
FIG. 18 is a section view of the assembly of the chuck.
DESCRIPTION OF PREFERRED EMBODIMENT
As shown in FIG. 1, an electrostatic chuck or clamp or fixture or
device 10 is provided. Chuck 10 includes a three-piece puck shaped
plate assembly or subassembly 12, and a bottom support 14.
As shown in FIGS. 2-11, subassembly 12 creates an electrostatic
field when energized, in order to clamp thereto a substrate (not
shown) during the substrate manufacture. Subassembly 12 and support
14 are connected by three bolts (not shown) and are coaxially
aligned along a chuck axis 20.
Plate subassembly 12 includes an inner coil portion or inner coil
38, which forms a top wall of a circular or doughnut-shaped inner
chamber 39, and includes an outer coil portion or outer coil 40
which forms bottom wall of chamber 41. A third chamber 43 is also
formed between subassembly 12 and support 14. As explained
hereafter passages interconnect chamber 39, 41 to chamber 43, after
assembly of inner coil 38 and outer coil 40 to main body 42.
As shown in FIGS. 2, 3, 4, inner coil 38 has an inner diameter of
44 of about 0.500 inches in this embodiment, and has an outer
diameter 46 of about 2.250 inches, and a thickness 48 of about
0.240 inches. Inner coil 38 also has two peripheral surfaces 47,
49, which have an electrical insulating coat or joint filler (not
shown). Inner coil 38 also has a bottom surface 50 and a top
surface 52. Top surface 52 has a ring groove 54 and has six inner
radial slots 56 and has six outer radial slot 58. Slots 56,58 are
respectively in radial alignment, in pairs, and have an equiangular
spacing. Slots 56, 58 are respectively disposed at angles of 30
degrees, and 330 degrees, thereby forming selectively shaped
surface portions therebetween. Bottom surface 50 has three inner
taped holes 60, on about 0.938 inch radius, with about a 0.120 inch
hole diameter, and at angles of about 90 degrees, 135 degrees, and
270 degrees.
As shown in FIGS. 5, 6, 7, outer coil 40 has an inner diameter 62
of about 3.240 inches in this embodiment, and has an outer diameter
64 of about 5.000 inches, and a thickness 66 of about 0.240 inches.
Outer coil 40 also has two peripheral surfaces 65, 67 which have an
electrical insulating coat or joint filler (not shown). Outer coil
40 also has a bottom surface 68 and a top surface 70. Top surface
70 has an outer ring groove 72 of about 4.500 inch diameter, and
has an inner groove ring 74 of about 3.700 inch diameter, and has
six radial interconnect slots 76. Slots 76 are disposed at angles
of about 30 degrees, ninety degrees 150 degrees, 210 degrees, 270
degrees and 330 degrees. Bottom surface 68 has two outer tapped
holes 78 on about 4.740 inch diameter at angles of 0 degrees and
180 degrees. Bottom surface 68 also has one other outer tapped hole
80 on a smaller diameter and at 135 degree angle and of 0.120 inch
diameter hole size.
As shown in FIGS. 8 through 11, main body 42 has a center hole 82
of about 0.100 inch hole diameter for gas passage, and has an outer
diameter 84 on about a 5.780 inch diameter, and has a thickness 86
of 0.740 inches. Main body 42 also has a bottom surface 88 and has
a top surface 90. Top surface 90 has an outer ring-shaped recess 94
for receiving outer coil 40, and has an inner ring-shaped recess 92
for receiving inner coil 38. Top surface 90 also has an inner
ring-shaped portion or projection 96, which is disposed between
recesses 92, 94. Projection 96 has six outer radial slots 102.
Slots 98, 102 are radially aligned, in pairs, at angles of 0
degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300
degrees. Bottom surface 88 has a spiral groove 104, and has two
outer holes 106 at angles of 0 degrees and 180 degrees, and has
three intermediate holes 110 at angles of 30 degrees, 150 degrees
and 270 degrees, and has two radially aligned holes 112, 114 at an
angle of 315 degrees.
Screw 16, which is identical to screw 18, has a length 116 of about
3.951 inches and has a head portion 117, and has a threaded end
portion 119.
As shown in FIGS. 13-17, support 14 has a wall 120, which has a
center hole 122. Wall 120 has a top surface 124, which has a recess
126, and has a bottom surface 128. Recess 126 has an inner diameter
130 of about 5.810 inches, and has a depth 132 of about 0.620
inches.
As shown in FIG. 15, recess 126 has two holes 134 with a hole
diameter of 0.100 inch, on a 4.392 inch diameter, at angles of 90
degrees and 270 degrees. Each hole 134 has a concentric groove 136.
As shown in FIG. 16, recess 126 has a ring groove 138. As shown in
FIG. 17, wall 120 has a projection 140 which has a ring groove 142.
Recess 126 also has three holes 144 on a 3.370 inch diameter at
angles of 0 degrees, 120 degrees and 240 degrees.
As shown in FIG. 18, the method of assembly of parts 38, 40 and 42
of subassembly 12 is indicated hereafter.
First, thread screw 16 into inner coil 38 and thread screw 18 into
outer coil 40.
Second, insert shoulder bolts 22, 24, 26, 28 through clearance
holes 106, 108, and install wafers 30, 32, 34, 36 on respective
bolts 22, 24, 26, 28.
Third, bed or dip coils 38, 40 into epoxy adhesive for filling
ring-shaped joints or gaps with epoxy adhesive.
Fourth, place coils 38, 40 in their respective pockets or recesses
92, 94.
Fifth, tighten shoulder bolts 22, 24, 26, 28 until coils 38, 40
touch their respective pairs of wafers 32, 34 and 30, 36.
Sixth, cure subassembly adhesive in an oven for about two hours at
a selective oven temperature.
As shown in FIG. 18, the method of assembly of the aforedescribed
subassembly 12 and the support 14 is indicated hereafter.
First, place subassembly 12 into recess 126 of support 14 after
placing seal rings in grooves 136 and 138.
Second, orient subassembly 12 about axis 20 relative to support 14
until holes 144 are aligned; and tighten tapped bolts in holes
144.
The materials of chuck 10 are indicated hereafter: a) Subassembly
parts 38, 40, 42, and support 14, are made of a metal such as an
anodized aluminum alloy;
b) Washers 30, 32, 34, 36 are made of an electrically insulating
material of a selective type to suit its bearing stresses and other
requirements, such as a plastic material or a ceramic material, for
forming bearing resistant separators;
c) The joints (not shown) adjacent to the inner and outer diameters
44, 46 of inner coil 38 and the inner and outer diameters 62, 64 of
outer coiled 40, are made of a selective material, such as a
curable adhesive material, or a like electrically insulating filler
material, for forming the four insulating rings;
d) Shoulder bolts 22, 24, 26, 28 are removable metal shoulder bolts
for assembly of the plate parts 38, 40, 42.
This embodiment of chuck 10 approximately meets the specification
as indicated hereafter;
a) Wafer size: 200 mm, 150 mm, 125 mm or 100 mm;
b) Temperature range: -60.degree. C. to 180.degree. C.;
c) Cooling gas pressure: 8 torr max;
d) Typical gas flow: 10 to 20 sccm;
e) RF electrode voltage: 200 pk volts max; and
f) Vacuum compatibility: to 1.6.times.10.sup.-7 torr.
This embodiment of chuck 10 has the features and benefits as
indicated hereafter:
a) It is an integral unit with adaptor flange; therefore, it is
easy to change chuck 10 to suit a new wafer size;
b) It has low temperature compatibility; therefore provides a cold
chuck application;
c) It has a low rate of flow of gas, and may use helium, argon or
nitrogen; therefore, it does not interfere with existing process of
manufacture;
d) It uses up to 8 torr backside pressure; therefore, it provides
efficient temperature control of wafer;
e) RF provision; therefore, it is adapted to integrate to a reactor
of an existing system; and
f) Low pressure compatibility; therefore, it has multiple
applications.
The advantages of chuck 10 are indicated hereafter:
a) The voltage for forming a suitable electrostatic field is
minimized as compared to the prior art electrostatic chuck;
b) The chuck 10 has a single plate assembly for forming the
electrostatic field, and having chambers and passages for cooling
the clamped substrate during manufacture;
c) The electrostatic field is uniform in value across the surface
of the plate unit 12, thereby minimizing the required voltage;
d) The electrostatic field causes clamping of the substrate to the
plate unit 12, from the substrate center radially outwardly to the
substrate peripheral edge, thereby preventing edge damage to the
substrate;
e) Sealing of the cooling system is facilitated; and
f) Chuck 10 has no moving parts, thereby reducing wear and gas
leakage.
While the invention has been described in its preferred embodiment,
it is to understood that the words which have been used are words
of description rather than of limitation and that changes may be
made within the purview of the appended claims without departing
from the true scope and spirit of the invention in its broader
aspects. For example, chuck 10 or support 14 can have a
conventional lift pin mechanism for robotic handling of the
wafer.
* * * * *